The present invention relates to an apparatus for measuring the quantity of hydrogen occluded in hydrogen occluding metal.
Hitherto, the quantity of hydrogen occluded in hydrogen occluding metal enclosed in a tank for accumulating hydrogen has been measured by measuring the pressure (the equilibrium pressure of hydrogen) in the tank. In accordance with the measured pressure, the quantity of occluded hydrogen, that is, the quantity of hydrogen stored in the tank has been estimated.
The foregoing method of estimating the quantity of hydrogen by measuring the pressure in the tank cannot accurately measure the quantity of hydrogen because a one-to-one relationship cannot easily be obtained between the pressure in the tank and the quantity of hydrogen.
The hydrogen occluding metal expands when it occludes hydrogen and contracts when hydrogen occluding metal discharges hydrogen. A method of estimating the quantity of hydrogen in the tank for accumulating hydrogen by measuring change in the volume of the hydrogen occluding metal by using the above-mentioned characteristic has been disclosed in Japanese Patent Laid-Open No. 6-249777. The change in the volume of the hydrogen occluding metal in the form of powder cannot be easily and directly measured. Therefore, the foregoing method includes the step of applying pressure to an optical fiber by expansion and contraction of the hydrogen occluding metal to indirectly measure the change in the volume of the hydrogen occluding metal in accordance with the change in light which passes through the optical fiber.
The foregoing method having the step of measuring change in the volume of the hydrogen occluding metal by using light, however, requires a structure which is too complicated.